Tech Tear Down

It’s been a good long while since I’ve really dissected a bit of electronics. But I finally got another chance after uncovering an old broken CD/radio/cassette player in the basement! After some tests, I determined that the CD player part of it didn’t work. Since no one uses archaic cassette tapes anymore, and a radio that weighs ten pounds is pretty impractical, I naturally snapped it up to tear it apart. 🙂

The boombox before dissection; note that it’s quite dusty. It was manufactured in 1997 so it was about 20 years old.

Disassembling it was pretty trivial. There was only a few screws which held the casing together, and each internal part also held in place with screws. The most challenging part was removing the large speakers. Each was both glued and screwed, so it took a little extra prying to get them off.

The boombox can be powered from both batteries and the house current, so there’s both a transformer and a large compartment to hold eight D cells. There’s one large PCB that combines the circuits for the CD player, cassette player, and radio player, with a few offshoot PCBs to connect the controls.

Finally I have a rather ambitious Tech Tear Down: an entire computer desktop case! It was sitting in the basement waiting to be disposed of, so naturally I decided to take it apart. The computer is a Dell Inspiron that runs Windows 7. I’m not sure why it was junked; I think there was some kind hardware problem. Because it has so many components inside, I’m dividing this TTD into a bunch of parts. First off is the CD-ROM drive!

The computer actually had two different CD- ROM drives. One of them was just a readable CD-ROM drive, and the other one was read/writeable, allowing you to burn CDs. Since both drives were still in working condition within the computer, I took apart the readable drive, and kept the read/write one to save in case I need to replace one in the future or maybe even build my own computer (or add it to my RasPi)!

The CD-ROM drives, each a metal rectangular box, had their own cubby in the computer case. They’re connected to the motherboard by just a ribbon cable. In the above picture, you can see the space in the case that they took up.

It was easy to take apart. The first thing to do was remove the metal casing on the back with a screwdriver. The rest of the components inside were either snapped or screwed in place, so it was just a matter of making good use of my screwdriver. The ‘motherboard’ PCB was right on top, with assorted ribbon cables connecting to the laser and the three motors. One motor ejects and closes the CD holder in a system of slides and gears, one spins the CD inside for the laser to read, and one moves the laser up and down using a screw mechanism.

Because I didn’t break or damage anything, I could theoretically put the whole disk drive back together again, but I don’t think that’ll happen. I found one of my mom’s long lost classical music CDs that was left in one of the drives. Luckily I like take stuff apart otherwise she would have lost it permanently! 🙂

My mom is obsessed with dehumidifiers. When one of the three in the house stopped working (it was old and in bad shape when we got it, so it was no surprise that it broke) I of course jumped on the opportunity to tear it up, even though my mom was upset. It was already partially apart when I got it, because my dad had been trying to fix it. I was most interested in the two PCBs inside.

One was the control board, attached near the top of the unit, that you could adjust the dehumidifier settings, such as the on/off time, desired humidity level, and fan speed. Another PCB buried deep within served to connect the rest of the mechanical parts of the unit to power. There’s some relays, a large cylindrical electrolytic cap, an even larger ‘boxy’ cap, and a transistor with a heat sink.

And finally, here’s a pic of my dog, Denver, next to the humidifier torn apart. The dehumidifier is medium sized as far as dehumidifiers go.

Time for an insides look at two old video game controllers: one from the Playstation 2 (2000), and one from the Sega Genesis System (early 1990s). The PS2 controller was not in working condition, so I completely teared it down, while the Sega Genesis controller still worked so I had to be more careful with it.

Because the two controllers were made about a decade apart, the Sega Genesis controller is extremely simple compared to the PS2 one. After removing the screws on the back, all there was inside was a PCB with capacitive buttons and one IC. Because the controller is completely digital (unlike the PS2), there’s really no need for the controller to have any other elements.

The PS2 controller was an entirely different story. It was jam packed with all sorts of stuff. First of all, the PS2 controller has analog joysticks that take up quite a bit of space up on the inside. There’s one PCB, to which a rectangular LED is soldered as well as multiple ICs. The PS2 controller also has a vibration affect, created by two DC motors with off-centered weights attached to them. Like the Sega Genesis Controller, the PS2 controller has digital capacitive buttons. What was interesting was how the little iconic x-o-square-triangle buttons popped out. I might be able to integrate them into a future electronics project!

Now I’m reverse engineering some power tools! Since my dad got a fancy new drill, he let me disassemble one of his old ones that he lacks a battery for.

Taking it apart was relatively easy. Once the big screws that held the two halves together were removed, the yellow shell popped apart. The inside of the drill was rather dirty, from years of dust and dirt entering through slits near the motor. The DC motor itself was large (about an inch in diameter), and hooked directly to trigger mechanism, which hooks to a rechargeable 12v battery. There was quite a few well-greased metal gears connected to the motor shaft that maximized the motion of the drill shaft.

I’m not exactly sure what I’m going to do with all the pieces, but the gears are pretty cool!

I found an old Philips TV remote and of course took it apart. Inside there was just a PCB underneath the rubber button mass. Each button is actually a capacitive sensor. When the rubber bottom of each button comes into contact with the cap, it changes the amount of capacitance. This signal from the remote is transmitted via an infrared LED that the TV picks up and decodes. The picture below shows the LED on the top of the PCB. It’s labeled IED1.

This is one of my strangest Tech Tear Downs yet… My dad, my brother, and I cleaned up our backyard, filling up a Bagster all the way to the top. We went through an old junk pile, and buried underneath everything and covered up with leaves and dirt was the electronic guts of an old electronic organ that we trashed sometime around 2007. I was of course extremely curious, and despite the dirt, I salvaged the bulk of the electronics to see what they we’re made of or course to see if there was anything useful.

Basically, there was four large PCBs stacked and bolted on top of each other. They consisted of diodes, transistors, resistors, and capacitors, as well as a few op amp ICs. Other than on the top layer, there was little corrosion on the components, and I wondered as to how useful they would be, considering that they’re from the 80s and they’ve been subject to very extreme temperatures, as well as water.

I was excited to see that there was loads and loads of diodes (the image above shows a section of one PCB after I removed a bunch of the diodes; they were easy to get to). I would estimate there was close to 80 silicon diodes that I could have used in a breadboard. I set a table and got out all my tools and spent a while removing the diodes and a few of the resistors, using mainly a small flat-head screw driver and needle-nosed pliers. I was able to get maybe 50 diodes, a few resistors, and a few transistors, as well as a few useless souvenir ICs.

I tested a few of the diodes out, and they worked great. The transistors were junk, and most of the resistors had leads that were too short. But now I have enough diodes to make a decimal-to-binary converter!

Above is where I was working.

There’s a few differences I noted between these four giant PCBs and modern day ones. First, the etched copper connections were very curvy, instead of rectangular and crammed together as you see on modern machine-made PCBs. Secondly, the wires coming off the PCBs weren’t directly soldered onto the board. Instead, a little metal spike pokes out of the board and the wire wraps tightly around the spike, so the joint is more mechanical, as you can see in the picture below.

Quite frankly, I don’t really know how these PCBs work inside the organ. They were labeled in a few spots as having something to do with ‘rhythm’ and there was a large mass of wires exiting the PCBs, so my guess is these boards were responsible for generating the different tones on the organ.